1. Field of the Invention
This invention relates to bone compression and distraction devices designed to compress or distract the ends of a fractured or cut bone. More particularly, this invention relates to bone compression and distraction devices which utilize an adjustment assembly in combination with a slotted plate.
2. Description of the Background Art
Presently, there exist numerous types of bone compression devices in which the ends of a fractured or cut bone are forced together by an adjustment assembly whereupon a permanent or temporary internal splint bar is affixed to securely retain the ends of the bone together. There also exist numerous types of bone distraction devices which allow a bone to be lengthened by cutting the bone and distracting the ends of the bones apart by the desired distance, affixing the ends in place with a permanent or temporary internal splint and filling the gap between the plated bone ends with a bone segment to facilitate growth across the spanned distance. Many devices are designed to be used both as a compression and a distraction device. U.S. Pat. Nos. 3,244,170, 3,604,414, 4,475,546, 4,187,841, 3,709,219, 2,333,033, EU No. 747,876, DL No. 206,074 and FR. No. 1,507,627 disclose various embodiments of bone compression and distraction devices.
East German Patent No. 206,074 and French patent No. 1,507,627 each disclose a bone compression device including an adjustment assembly designed to be used in combination with a slotted plate. More particularly, the adjustment assembly comprises a stationary block and a moveable block interconnected by a threaded adjustment. The slotted plate includes a pair of screw holes at one end and a slot at another screw hole at the other end. Screws are placed through the pair of screw holes to rigidly affix the one end of the plate to one end of the bone. The stationary block of the adjustment assembly is affixed to the one end of the plate and the moveable block is affixed to the bone at the other end of the plate through the slot either by means of a pin inserted through the slot into the end of the bone (French patent) or by means of a claw which engages the head of a screw positioned through the slot and into the end of the bone (German Patent). Operation of the threaded adjustment of the adjustment assembly causes the moveable block to slide toward the stationary block thereby compressing the ends of the bone together. Once compressed, screws are positioned in the screw hole and the slot at the other end of the plate, thereby rigidly securing the ends of the bone together.
U.S. Pat. No. 3,244,170 discloses a similar bone compression device including a tension device for use in combination with a slotted plate. In this patent, the slotted plate includes a slot at both of its ends through which screws are inserted for threaded engagement with the respective ends of the bone. The adjustment assembly engages the heads of the screws and, upon operation, forces the screws together thereby compressing the ends of the bone together. Once compressed, permanent screws are inserted into screw holes in the plate while the adjustment assembly retains the ends of the bone under compression. After the screws are securely tightened, the adjustment assembly is removed.
Several disadvantages are noted with respect to the above referenced bone compression and distraction devices. First, the patents referenced above illustrate the bone screws engaging through only one cortex of the bone. Further, the adjustment assembly is positioned substantially off axis from the axis of the bone being compressed or distracted. Thus, an excessive force is exerted by the adjustment assembly which may result in the bending of the bone screw or toggling of the bone screw in the bone thereby weakening the connection of the adjustment assembly to the bone under compression or distraction. Additionally, the adjustment assembly's use of a pin (French Patent) or a claw (German Patent) may result in scoring of the slotted plate should the pin or claw slip during use. The scoring of the plate could then result in crevice corrosion.
Finally, some of the devices disclosed above do not provide for both compression and distraction of a bone. Without both features, the difficulty of inserting a bone segment during the lengthening of the bone is increased since the ends of the bone cannot be compressed to retain the bone segment therebetween. Additionally, recutting or reshaping of the ends of the bones is not easily accomplished without both features of both distraction and compression.
Therefore, it is an object of this invention to provide an apparatus which overcomes the aforementioned inadequacies of the prior art devices and provides an improvement which is a significant contribution to the advancement of the bone distraction and compression art.
Another object of this invention is to provide a new and improved bone compression and distraction device including an adjustment assembly designed for use in combination with a slotted plate, the device operable as a compression device and/or a distraction device.
Another object of this invention is to provide a bone compression or distraction device including a slotted plate and an adjustment assembly, the adjustment assembly having a stationary block and a moveable block interconnected by a threaded adjustment, the blocks having a transverse hole allowing bone screws to be inserted therethrough and then through a hole and a slot, respectively, in the slotted plate for threading into the respective ends of the bone thereby minimizing the inadvertent scoring of the slotted plate.
Another object of this invention is to provide a bone compression or distraction device including an adjustment assembly which produces a compressive or distractive force adjacent to the axis of a bone being compressed or distracted, thereby minimizing bending, toggling, or otherwise weakening of the bone screws in the bone.
Another object of this invention is to provide a bone compression or distraction device which allows the removal of a segment of bone from a long bone of the forearm (ulna) while being held in original rotational orientation by means of a slotted plate and which can then be operated to compress the two ends of the bone together to then be held in place by means of additional bone screws positioned through the plate, thereby shortening the entire length of the bone.
The foregoing has outlined some of the more pertinent objects of the invention. These objects should be construed to be merely illustrative of some of the more prominent features and applications of the intended invention. Many other beneficial results can be obtained by applying the disclosed invention in a different manner or modifying the invention within the scope of the disclosure. Accordingly, other objects and a fuller understanding of the invention may be had by referring to the summary of the invention and the detailed description of the preferred embodiment in addition to the scope of the invention defined by the claims taken in conjunction with the accompanying drawings.